Piercing valve stem assembly



FIG. 1 is a perspective view of a piercing valve stem assembly showingmy new design;

FIG. 2 is a front plan view thereof, the rear, top and bottom beingmirror images;

FIG. 3 is a left plan view thereof; and,

FIG. 4 is a right plan view thereof.

CLAIM The ornamental design for a piercing valve stem assembly, as shownand described.